[LTP] [PATCH v1 1/2] Ensure prio is within valid range in `rt-migrate.c`

[Andrea Cervesato]

Hi!

  I generally suggest to refactor test into new API if a structural 
change is needed. Here we are in a grey zone, because the test is old 
enough to be refactored and patch isn't so big. Still, test is bugged 
and we need to fix _at least_ a small portion of it.

I would suggest to take a look at the code a bit closer and to guess how 
much effort we should put in order to rewrite it with new API. The test 
seems pretty simple, if we get rid of all the old stuff (options, stdout 
management) as we supposed to do anyway.

Regards,
Andrea

On 9/12/23 16:43, Marius Kittler wrote:
> * According to the documentation the value param->sched_priority
>    must lie within the range given by sched_get_priority_min(2) and
>    sched_get_priority_max(2). This change ensures that this is the
>    case without completely restructuring the test yet.
> * See https://github.com/linux-test-project/ltp/issues/812
>
> Signed-off-by: Marius Kittler <mkittler@suse.de>
> ---
>   .../realtime/func/rt-migrate/rt-migrate.c     | 21 ++++++++++++++-----
>   1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/testcases/realtime/func/rt-migrate/rt-migrate.c b/testcases/realtime/func/rt-migrate/rt-migrate.c
> index 97ab604c7..2554f63e2 100644
> --- a/testcases/realtime/func/rt-migrate/rt-migrate.c
> +++ b/testcases/realtime/func/rt-migrate/rt-migrate.c
> @@ -74,6 +74,9 @@
>   
>   #define VERSION_STRING "V 0.4LTP"
>   
> +#define CLAMP(x, lower, upper) (MIN(upper, MAX(x, lower)))
> +#define CLAMP_PRIO(prio) CLAMP(prio, prio_min, prio_max)
> +
>   int nr_tasks;
>   int lfd;
>   
> @@ -137,7 +140,7 @@ static unsigned long long interval = INTERVAL;
>   static unsigned long long run_interval = RUN_INTERVAL;
>   static unsigned long long max_err = MAX_ERR;
>   static int nr_runs = NR_RUNS;
> -static int prio_start = PRIO_START;
> +static int prio_start = PRIO_START, prio_min, prio_max;
>   static int check = 1;
>   static int stop;
>   
> @@ -284,8 +287,8 @@ static void print_results(void)
>   	printf("Parent pid: %d\n", getpid());
>   
>   	for (t = 0; t < nr_tasks; t++) {
> -		printf(" Task %d (prio %d) (pid %ld):\n", t, t + prio_start,
> -		       thread_pids[t]);
> +		printf(" Task %d (prio %d) (pid %ld):\n", t,
> +			   CLAMP_PRIO(t + prio_start), thread_pids[t]);
>   		printf("   Max: %lld us\n", tasks_max[t]);
>   		printf("   Min: %lld us\n", tasks_min[t]);
>   		printf("   Tot: %lld us\n", tasks_avg[t] * nr_runs);
> @@ -394,6 +397,13 @@ static void stop_log(int sig)
>   
>   int main(int argc, char **argv)
>   {
> +	/*
> +	 * Determine the valid priority range; subtracting one from the
> +	 * maximum to reserve the highest prio for main thread.
> +	 */
> +	prio_min = sched_get_priority_min(SCHED_FIFO);
> +	prio_max = sched_get_priority_max(SCHED_FIFO) - 1;
> +
>   	int *threads;
>   	long i;
>   	int ret;
> @@ -448,7 +458,7 @@ int main(int argc, char **argv)
>   
>   	for (i = 0; i < nr_tasks; i++) {
>   		threads[i] = create_fifo_thread(start_task, (void *)i,
> -						prio_start + i);
> +						CLAMP_PRIO(prio_start + i));
>   	}
>   
>   	/*
> @@ -460,7 +470,8 @@ int main(int argc, char **argv)
>   
>   	/* up our prio above all tasks */
>   	memset(&param, 0, sizeof(param));
> -	param.sched_priority = nr_tasks + prio_start;
> +	param.sched_priority = CLAMP(nr_tasks + prio_start, prio_min,
> +								 prio_max + 1);
>   	if (sched_setscheduler(0, SCHED_FIFO, &param))
>   		debug(DBG_WARN, "Warning, can't set priority of main thread!\n");
>   	intv.tv_sec = INTERVAL / NS_PER_SEC;